Dellorto SH1/20 set up help

[jon]

Please can anyone advise on correct jetting for a dellorto SH1/20 running a sx200 with 42mm clubman & cam lam fast flow air filter?

Many thanks, Jon

[rog60]

Just out of curiosity, do you have a problem with the 'standard' jetting?
I would have thought that as you are probably getting a better airflow then you should increase the main jet size by about two sizes at least! This is a case of (if you have a problem,i.e Weak mixture) of obtaining a suitable selection of jet sizes above that fitted and trying them out one at a time until plug colour/performance is satisfactory..........

[jon]

Thanks rog60. Seems to run fine at low revs/speed with the standard 48 pilot & 103 main with plug colour being about right. But when I went full throttle for about 5 minutes it started to slow as if a heat seize was about to happen. Slowed it down immediately & went slowly on back roads & all was ok. Have since tried running a 50 pilot & 110 main which at low revs judders as if running on choke but at full throttle goes well. There was much more black/oily residue coming through exhaust & plug was blacked/fouled. Have swapped back to 48 pilot with a 108 main but have not been able to get out yet. Will let you know what happens. Many thanks

[rog60]

Thanks rog60. Seems to run fine at low revs/speed with the standard 48 pilot & 103 main with plug colour being about right. But when I went full throttle for about 5 minutes it started to slow as if a heat seize was about to happen. Slowed it down immediately & went slowly on back roads & all was ok. Have since tried running a 50 pilot & 110 main which at low revs judders as if running on choke but at full throttle goes well. There was much more black/oily residue coming through exhaust & plug was blacked/fouled. Have swapped back to 48 pilot with a 108 main but have not been able to get out yet. Will let you know what happens. Many thanks

If your engine slows down when opening the throttle then accelerates if you reduce the throttle then that's a sure sign of weak mixture (will seize/hole piston if you persist). Also what seems to work fine when pootling around will be a weak mixture when at much higher speeds. What you need is a happy medium i.e a little rich at low rpm but OK at higher revs. Sounds like 48 pilot and 110 main may be the right combination.

Carbs run with pilot jet/progression system for up to 3/4 throttle then go onto main jet only to full throttle.

[jon]

Thanks very much for the advice.

Will try a 110 main again with a 48 pilot & see what happens.

Cheers